Southern California -- this just in

Anticipation is building for Sunday night's landing of the rover Curiosity on the surface of Mars.

In a Google + Hangout, Times reporters Scott Gold and Amina Kahn talked about the mission with Ashwin R. Vasavada, a deputy project scientist at the Jet Propulsion Laboratory in La Canada Flintridge.

He talked about the great anticipation that comes with the mission.

"If this goes well Sunday, we won't know what to do with ourselves," he said during the chat.

Curiosity, a roving lab that will scour Mars for the ingredients of life, is scheduled to land at 10:17 pm PDT Sunday in an ancient geological feature known as the Gale Crater. It is a complex operation. At 1,982 pounds, Curiosity is five times heavier than previous Mars rovers. Its landing requires a dizzying sequence of pyrotechnics and on-the-fly adjustment, all done automatically because Mars is 154 million miles away, too far for the swift communication needed to guide the landing from Earth.

On Thursday, scientists revealed that Curiosity has already delivered results, even before it lands.

Curiosity's instruments are expected to yield a new understanding of Mars' history and environment. The mission's impact doesn't end there, however. Curiosity is also expected to pave the way for future Mars missions, including the first human exploration. President Obama has set a goal of sending an astronaut to Mars by the 2030s.

That would be no small matter. Rather than the three days it took to reach the moon, an astronaut would endure a nine-month trip there and then another one to get home. Scientists are still trying to understand how they might guard against radiation that astronauts would encounter. It's a critical issue. Carrying a proper radiation shield would be both vital and burdensome.

Curiosity was equipped with a device, known as RAD, to measure radiation once the craft arrives. Mars, because of its thin atmosphere and weak magnetic field, lacks the ability to repel or absorb radiation, a trait that could have affected the planet's ability to foster life.

About a year ago, scientists realized they could turn RAD on early -- that they didn't need to wait for Curiosity to get to Mars. The instrument was turned on 10 days after launch and was active for most of the spacecraft's 8 1/2-month journey to Mars. It has already sent home a significant amount of data.

RAD measured radiation encountered by Curiosity along the way, both outside the craft and inside, where an astronaut would be housed during a human-exploration "cruise."

Though scientists are still digesting the data, early indications are that radiation outside the spacecraft carrying Curiosity was perhaps 100 times higher than inside the craft. Still, levels inside might have been a full fifth of the amount of radiation that NASA allows its astronauts to face over the course of their career — "not a full, lifetime dose, but not insignificant," said Don Hassler, RAD's principal investigator. A better understanding of deep-space radiation could help determine everything from spacecraft construction to when a human-exploration mission might launch to limit an astronaut's exposure.